Somatic embryogenesis in the leaf tissue of Hedyotis diffusa Willd.

Hedyotis diffusa is a valuable medicinal herb belong to the Rubiaceae family. It is widely used in the treatment of various types of cancer and other diseases related to leukemia. Besides, the plant usually contains triterpenoids (oleanolic acid, ursolic acid) and flavonoids which have a range of pharmacological activities of antiinflammatory, antibacterial, hypoglycemic, antifree radicals, reducing blood lipids and anticancer. Leaf segments of 3 weeks old H. diffusa were cultured on half strength Murashige and Skoog (½MS) medium supplemented with different concentrations of indole acetic acid (IAA; 0.1, 0.2 and 0.4 mg/L) or α-naphthalene acetic acid (NAA; 0.1, 0.2 and 0.4 mg/L) and benzyladenine (BA) at a concentration of 1mg/L. In this study, the highest percentage of somatic embryogenesis was obtained using 0.1 mg/L IAA and 1 mg/L BA, and 0.2 mg/L IAA and 1 mg/L BA. The somatic embryos develop through a series of morphological stages: globular type, heart, torpedo and mature embryos. Besides, the highest number of shoots per explant was achieved in the same media. The middle and the distal end segments were found the most suitable for somatic embryogenesis. Morphological changes and the role of endogenous hormones in somatic embryo formation were analyzed. The position of the leaf segments of the same leaf, respiration rate, and endogenous hormone and somatic embryo formation were also discussed.